Controlling quantum tunneling with light

Scientists at the Cavendish Laboratory in Cambridge have used light to help push
electrons through a classically impenetrable barrier. While quantum tunneling
is at the heart of the peculiar wave nature of particles, this is the first
time that it has been controlled by light. Their research is published in Science.

Particles cannot normally pass through walls, but if they are
small enough quantum mechanics says that it can happen. This occurs during the
production of radioactive decay and in many chemical reactions as well as in
scanning tunneling microscopes.

According to team leader, Professor Jeremy Baumberg, "the trick
to telling electrons how to pass through walls, is to now marry them with
light."

This marriage is fated because the light is in the form of
cavity photons, packets of light trapped to bounce back and forth between
mirrors which sandwich the electrons oscillating through their wall.

Research scientist Peter Cristofolini added: "The offspring of
this marriage are actually new indivisible particles, made of both light and
matter, which disappear through the slab-like walls of semiconductor at will."

One of the features of these new particles, which the team
christened 'dipolaritons,' is that they are stretched out in a specific
direction rather like a bar magnet. And just like magnets, they feel extremely
strong forces between each other.

Such strongly interacting particles are behind a whole slew of
recent interest from semiconductor physicists who are trying to make
condensates, the equivalent of superconductors and superfluids that travel
without loss, in semiconductors.

Being in two places at once, these new electronic
particles hold the promise of transferring ideas from atomic physics into
practical devices, using quantum mechanics visible to the eye.